jSa Barrett, Expedition to Capricorn Group. [ist^Dec 



Lady Elliott Island," is divided from North- West Island, as it 

 were, by the imaginary line of the tropic. On clear days the 

 blue peaks on the mainland were visible from the islands, 

 and the smoke of steamers — grey feathers drifting along the 

 horizon — was frequently seen by the marooned ornithologists. 

 A quotation from Mr. Hedley's paper may be fittingly intro- 

 duced : — 



" Strictly speaking, this group (the Capricorns) is not part of 

 the Great Barrier, which terminates in a coral maze, Swain Reefs, 

 north of the Capricorns. Between Swain Reefs and the Capri- 

 corns lies the broad and deep Curtis Channel, but for zoological 

 purposes these pseudo-atolls may conveniently be regarded as a 

 continuation of the Great Barrier." 



His description of the Mast-Head Island reef may be taken as 

 fairly typical of what was observed at each island visited by the 

 R.A.O.U. expedition : — 



" At low tide Mast-Head is exposed as an oblong reef about 

 4 miles from east to west, and li from north to south, its crest 

 10 or 12 feet above the sea. It shrinks at high water to a small 

 but densely vegetated sand-bank about loo acres in extent, 

 placed near the western end of the reef. The islet is level, raised 

 but a few feet above the sea, and has no lagoonlet. Concentric 

 undulations show the successive increase of beach built on beach. 

 At the western end a clump of uprooted casuarinas indicates where 

 a gale had inflicted temporary loss. 



"■ On the south side a stratum of coral sand-rock is now suffer- 

 ing denudation. Jukes * has given an excellent description and 

 explanation of this rock. ... I suggest that the coral sand- 

 rock can only form beneath a thick cover of sand, and that slow 

 growth of the bank will provide for the increase of the rock. 

 Briefly, the coral sand-rock is the petrified core of beach or dune. 

 The islet was chiefly made of coarse sand. It may be laid down 

 as a rule that the further from the reef edge an islet is btiilt, the finer 

 are the materials of which it is composed. A pit we sank in search 

 of water passed through foraminiferal sand with lumps of coral ; 

 it was bone dry at a depth of 8 feet. There was no surface water 

 at the date of our visit." 



The Reef. 



Further on in his paper Mr. Hedley describes the reef and its 

 wonders. The reef crest, he finely says, is " one long unbroken 

 sepulchre of actinozoan life." There were marine biologists with 

 No. 2 party, and the reef received close attention from them ; 

 but with the results of their work an ornithological journal is not 

 concerned. Mr. Hedley's comparison of Mast-Head Reef with 

 the real coral atoll is, however, pertinent in a general narrative of 

 the expedition : — 



" Mast-Head Reef, though sharing many features of the coral 

 atolls of the Central Pacific, yet differs widely in detail — a differ- 



* Jukes, " Voy. /v'j'," i. (184"), pp. 7, 9. 



